OneNote - Get the OneNote app for free on your tablet, phone, and computer, so you can capture your ideas and to-do lists in one place wherever you are. Or try OneNote with Office for free.
PiP for Mac - Always on top window preview similar to the popular windows only OnTopReplica
Evernote - Bring your life's work together in one digital workspace. Evernote is the place to collect inspirational ideas, write meaningful words, and move your important projects forward.
Helium - Helium lets you accept payments by credit card for anything you want to sell online.
Joplin - Joplin is a free, open source note taking and to-do application, which can handle a large number of notes organised into notebooks. The notes are searchable, tagged and modified either from the applications directly or from your own text editor.
X-Mouse Button Control - XMouse Button Control (XMBC) allows you to create application and window specific profiles.